Skip to main content

View Diary: Historic SpaceX Launch Scheduled for Tomorrow Morning (+Sweet Rocket Pics) (30 comments)

Comment Preferences

  •  Definitely (1+ / 0-)
    Recommended by:
    Troubadour

    It'd be Bad to launch retrograde. I am not aware of any satellite that is in an equatorial retrograde orbit, although there are some that are near-polar which are in a retrograde orbit (these are known as sun-synchronous satellites).

    •  How does one define a retrograde polar orbit? (0+ / 0-)

      You mean the orthogonal component is toward the West, or is there some arbitrary prograde direction in polar orbits?

      Always apart, always asking Why.

      by Troubadour on Sat Sep 28, 2013 at 02:23:05 PM PDT

      [ Parent ]

      •  ns (1+ / 0-)
        Recommended by:
        Troubadour

        Not polar, but rather "near" polar, i.e. inclinations around 87 degrees or so. One could consider such orbits as "posigrade" orbits with an inclination of 93ish degrees, but orbital mechanics buffs would stab ya :) Inclination is usually defined in the range of -90 < i < 90 degrees, so exceeding that range in either direction just makes an ordinarily-posigrade orbit into a retrograde orbit.

        •  So it is just the equatorial component (0+ / 0-)

          that defines pro/retrograde in a polar context?

          Always apart, always asking Why.

          by Troubadour on Sat Sep 28, 2013 at 03:20:29 PM PDT

          [ Parent ]

          •  Yep! (1+ / 0-)
            Recommended by:
            Troubadour

            I'm not sure what they call perfectly polar orbits, though. I think they just use the inclination to differentiate between a south-->north orbit or a north-->south orbit. One would have 90 degrees (the north-->south one) and the other -90 degrees (south-->north).

            But one interesting tidbit is that a sun-synchronous satellite would not be sun-synchronous if it had an orbital inclination of 87 degrees. They have to be retrograde, otherwise the effect they're exploiting would no longer work. So in other words, I can't imagine why we'd want to launch something into an 87 degree orbit!

            •  The geometry of that escapes me. (0+ / 0-)

              I'll just take your word for it.

              Always apart, always asking Why.

              by Troubadour on Sat Sep 28, 2013 at 03:40:57 PM PDT

              [ Parent ]

              •  ns (1+ / 0-)
                Recommended by:
                Troubadour

                Well, it's exploiting the obliquity of the Earth in order to change the orbit's right ascension of the ascending node in such a way that the vector normal to the orbital plane does not change its orientation with respect to the sun. (This change in the right ascension happens in all orbits, so they feel that they might as well exploit it if they want to keep a satellite perpetually in sunlight or something.)

Subscribe or Donate to support Daily Kos.

Click here for the mobile view of the site